Vent cap



July 21, 1959 J. E. BUSKIRK VENT CAP Filed NOV. 12, 1957 SURFACE "A A Fig.

INVENTOR. John E Husk/7k BY His Af/om e y United States Patent VENT CAP John E. Buskirk, Munlcie, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 12, 1957, Serial No. 695,663 4 Claims. (Cl. 136-177) This invention relates to vent caps for storage battery, cells and more particularly to a vent cap of a snap-in type made of semi-rigid plastic material having a dilferent coefficient of expansion than material of which a battery case vent well is made.

It is therefore an object of the present invention to provide a battery vent cap having a dual and concentric skirt portion adapted to encase a vent well on opposite sides with semi-rigid plastic so that a seal will occur along an inside Well top surface during skirt portion expansion at high temperatures and along an outside well top surface during contraction at low temperatures rather than a seal obtained using a screw fit.

In carrying out the above object, it is a further object of this invention to provide complementary snap-ring portions of one of dual vent cap skirts engageable to lock relative to an inside well top surface while a rigid annular member with a central vapor inlet and electrolyte drain-off opening serves as a base for the vent cap and maintains diametric dimensions of the one skirt such that snap n'ng portions remain in engagement during either expansion or contraction when either inside or outside vent well sealing occurs respectively.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the. accompanying drawing, wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

Figure l is a top plan view of astoragebatte'ry equipped with a vent cap in accordance with the present invention.

Figure 2 is an enlarged, fragmentary cross sectional elevational view taken along line 2-2- of Figure l.

Vent caps, sometimes called vent plugs, are provided for storage battery cells to permit relief of excess pressure of gases which must be emitted from the cell and to permit testing and filling of thebattery with liquid, such as acid, water, orbotli; Figure 1 illustrates a" storage battery generally"indicated'bynumeral and including a series of cells 11; 12 and I3 electrically connected and contained in a casing 14' of acid-resistant material such as hard rubber or the like having a difierent coefiicient of expansion than semi-rigid plastic material used for vent caps generally indicated by numeral 16. Vent caps 16 of this invention are preferably made of a resilient material, such as polyethylene or other synthetic resilient plastic which is acid resistant and does not age harden appreciably and can be snap fitted or forced into a filler hole opening of a cell cover 18 to seal the cell against spilling or leaking of electrolyte.

A filler opening 19 is shown in the fragmentary sectioned view of Figure 2 along with a vent well generally indicated by numeral 20. The vent well 20 is formed of acid-resistant material such as hard rubber or the like integral with cover 18 and having a coefiicient of expansion like that of casing 14 but differing from the coefficient of expansion of the material used for the vent cap 16. The well includes an upwardy extending cylin- 2,896,007 Patented July 21, 1959 drical portion 22 having an inside top well surface 22a and an outside top well surface 22b. These inside and outside surfaces extend concentrically relative to each other for sealing engagement relative to complementary cylindrical surfaces AA and BB of outer skirt 23 and inner skirt 24 of the vent cap having axial or longitudinal dimensions AA' and B-B respectively as outlined by projections to the right in Figure 2. Upper cylindrical portion 22 of the Well vent opening 19 is encased on opposite sides by the semi-rigid plastic skirts 23 and 24 of the vent cap. Inner peripheral surface BB of skirt 23 is smaller in area than outer peripheral surface AA of skirt 24.

Skirts 23 and 24 are joined to each other above a top edge 25 of cylindrical portion 22 by an annular downwardly extending lower body portion 26 which is integral with a top cover or inverted dish-shaped upper body por-' tion 28 of vent cap 16. Integral with andextending downwardly from the upper body portion 28 is a cylindrical baffle generally indicated by numeral 30. Baffle 30 extends concentrically withinlower body portion 26 and skirts 23-24 to a location terminating inside the vent cap at a point below a bottom peripheral edge 23b of skirt 23 and above a bottom peripheral edge 24a-of skirt 24.

A rigid member or disc 32 of phenol formaldehyde, acid-resistant material, or the like is provided to serve as a base for the vent cap and has a vapor inlet and electrolyte drain-off passage 33 centrally located therethrough. Disc 32 has an outer diameter greater than that of an inner surface of skirt 24 which is provided with a groove or recess 34 having a diameter slightly greater than that of disc 32 but less than or substantially equal to a radial inner diameter of an annular ridge or abutment 36 pro truding from upper cylindrical portion 22. This abutment is complementary with a groove or recess 36a provided around surface AA of skirt 24. When skirt 24 is forced into filler opening 19, the abutment 36 and groove 36a are resiliently engaged and disc 32 assures locking'of the surface 22 a positively in sealed relationship to surface.

AA of skirt 24 as well as maintenance of engagement of abutment 36 relative to recess 36a.

The vent cap cover portion 28 has an exhaust vent or opening 38 located radially outwardly of baffle 30 on one side. Serving as a baffle to shieldpassage 33 against acid splash is a downwardly extending cylindrical portion 39 around filler opening 19. Fumes and any acid splash passing through passage 33 into an inner chamber 40 inside baffie 30 of thevent cap are necessarily reversed in directionof flow back to the base or disc 32 and little, if any, liquid ever passes into an outer annular chamber 42 leading to exhaust vent 38 which is located extending through cover portion ZS radially outwardly of annular bafile 3i) During variation of ambient temperature alfecting' either expansion or contraction of both the cell wall and vent well as well as the vent cap at different rates, previous semi-rigid plastic vent caps have not been practical due to difference in coefilcient of expansion (or contraction) of plastic and hard rubber, for example. Using the vent cap of the present invention, a more positive seal is obtained concurrently with either dissimilar expansion or contraction due to the structure described above. By encasing the vent well on both sides with semirigid plastic, a seal occurs between inside surface 22a of upper cylindrical portion 22 and outside surface AA of skirt 24; a similar seal occurs between outer surface 22b of upper cylindrical portion 22 and inner surface BB of skirt 23 during contraction at low temperatures. In either event, locking of abutment 36 with groove 36a combined with placement of disc 32 in groove 34 of skirt 24 further assures positive snap-in fitting of the vent cap relative to filler opening 19 but especially so during expansion at high temperatures when rigid member or disc 32 keeps peripheral edge 24a of skirt 24 at a proper diameter dimension to guarantee locking of abutment 36 relative to groove 36a. The advantages of having vent cap or plug skirts on both sides of cylindrical portion 22 of the cell cover as well as the interlocking snap fit of abutment 36 and groove 36a are apparent from the above description and drawing. The vent cap of the present invention is inexpensive to fabricate and also eliminates any necessity for progressive threading in the cell cover and vent cap. A tight, sliding, and positive seal is obtained as the vent cap of the present invention is snapped into place to stay under many and all operating conditions completely free of loosening and/ or loss of screw-type vent caps where acid spray leaking out of the filler opening will cause corrosion of compartments surrounding the battery.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A vent cap for use in combination with a storage battery cell cover which includes a filler opening surrounded by an upwardly extending cylindrical portion, comprising, a coverand downwardly extending body for the vent cap made of semi-rigid plastic material having a coetficient of expansion difierent than that of material of the cell cover and cylindrical portion, a pair of concentrically spaced skirts extending downwardly from said body and encasing both sides of the cylindrical portion with semi-rigid plastic material, the outer of said concentric skirts sealing against a top outer surface of said cylindrical portion during expansion at higher temperatures and the inner of said concentric skirts being of greater length than the outer skirt and sealing against a top inner surface of said cylindrical portion during contraction at lower temperatures, snap-in abutment means engaged between said inner concentric skirt and said cylindrical portion, and an annular rigid member fitted inside said inner skirt for maintaining engagement of said snap-in means.

2. A vent cap for use in a storage battery cell cover opening variable in size due to difierence in coeflicients of expansion of material used for the vent cap and cell cover, comprising, a body of polyethylene or the like, material forming the vent cap with a cover portion having an exhaust vent located intermediate a downwardly extending annular baffie and a downwardly extending lower body portion, a pair of concentric skirts projecting downwardly from said lower body portion for encasing opposite sides of an upwardly protruding cylindrical portion of the cell cover, locking means between one of said skirts which is longer than the other of said skirts and the cylindrical portion of the cell cover, and a disc engaging a periphery of one of said skirts for assuring maintenance of engagement of said locking means during sealing of either of said skirts relative to said cylindrical portion upon expansion or contraction at difierent rates in the cell cover and said vent cap.

3. A snap-in type vent plug of polyethylene material for use in sealing peripherally about a cylindrical portion of a hard rubber well cover having a filler opening therethrough, comprising, a top cover portion with an exhaust vent and a downwardly extending body portion,

said body portion including a pair of downwardly extending skirts to encase the cylindrical portion of the well cover on both sides with polyethylene material sealing surfaces, the sealing surface of the outer of said pair of skirts being shorter in length and less in area than that of the inner of said pair of skirts which extends longer to a lower level relative to the cylindrical portion of the well cover, a radial groove and abutment cooperable in a snap-fit between the inner of said skirts and the cylindrical portion, and a disc of rigid material secured inside the inner of said skirts below the level of said outer skirt and maintaining skirt diameter preventing upward sliding of said inner skirt relative to the cylindrical portion and maintaining engagement of said abutment relative to the radial groove, said disc serving also as a base for said vent plug and having a vapor inlet and electrolyte drain-off passage therein.

4. A snap-in type vent plug of semi-rigid plastic for use in sealing peripherally about a cylindrical portion surrounding an opening of a battery well cover of material with a coelficient of expansion different than that of the semi-rigid plastic, comprising, a plug body including a cover portion and an integral downwardly extending body portion, said body portion having inner and outer skirts with surfaces to encase both sides of the well cover cylindrical portion, an annular baflle integral with and extending downwardly from said cover portion and located radially of an exhaust vent in the cover portion, a disc made of material more rigid than that of said plug body and having a vapor inlet and electrolyte drain-ofl opening spaced remote from said battle and exhaust vent, said disc backing up the inner of said skirts radially for sealing a surface greater than a surface of said outer skirt against the cylindrical portion, and a snap-in locking abutment and complementary groove provided for engagement of said inner skirt and cylindrical portion, said skirts alternately sealing against the cylindrical portion in response to difierences in rates of expansion and contraction of materials of the well cover and vent plug, said inner skirt being longer than said outer skirt.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,400 Tupper Nov. 8, 1949 2,658,100 Kendall Nov. 3, 1953 2,682,568 Stofen June 29, 1954 2,695,115 Roop Nov. 23, 1954 2,810,777 Brandt Oct. 22, 1957 2,835,720 Buskirk May 20, 1958 

